The next time you buy SS parts for the boat, take along a weak magnet. If it pulls on the magnet, move onto the more expensive brand.

The ones you have are probably Seafit/Westmarine and not Attwood.

__________________Faithful are the Wounds of a Friend, but the Kisses of the Enemy are Deceitful! ........
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Unprepared boaters, end up as floatsum!.......

...It also looks like a very lightweight, Chinese crap-stainless part.

Definitely the bargain brand.

This.

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Counter sunk bolts where there is marginal support to sides is also very bad practice. I cringe when I see that, particularly on cast fittings. A wedge, flexing the weakest point, every time it is loaded. When fabricating parts that is something I strenuously avoid. Had it been designed for Flathead bolts the story might be different.

it could be IGA, those cleats are cast and don't have a lot of meat around the bolt, so it could be it had a micro crack before you tightened it and not IGA too. Simple cast material can be a bit crack prone in tension. I like chromed bronze or bronze in those herreschoff type cleats... but have used the cast 316 ss before too. I doubt cast SS will react to a magnet..?
I like those style cleats but most manufacturers (US or orient) seem to leave little meat around the bolt hole. I'd like to see at least 2 x the hole diameter all around the hole. No one makes that that I know of.
So you are stuck with a cleat that has two bolts going thru it, or this type with 4 bolts and little edge margin...

__________________"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard

The next time you buy SS parts for the boat, take along a weak magnet. If it pulls on the magnet, move onto the more expensive brand.

The ones you have are probably Seafit/Westmarine and not Attwood.

Hey Del, In my mind most Atwood stuff is cheap pot metal hardware. That aside.. Do they actually make these Herreschoff cleats in the USA? I would seriously doubt that ....but it would be good to know if anyone knows!

__________________"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard